SEOUL, South Korea (AP) — North Korea may postpone the controversial launch of a long-range rocket that had been slated for liftoff as early as Monday, North Korean state media said Sunday.

Scientists have pushed forward with preparations for the launch from a west coast site but are considering “readjusting” the timing, a spokesman for the Korean Committee for Space Technology told North Korea’s state-run Korean Central News Agency.

It was unclear whether diplomatic intervention or technical glitches were behind the possible delay. The brief statement cited “some reasons” but provided no further details.

North Korea announced earlier this month that it would launch a three-stage rocket mounted with a satellite from its Sohae station southeast of Sinuiju sometime between Dec. 10 and Dec. 22. Pyongyang calls it a peaceful bid to send an observational satellite into space, its second attempt this year.

The United States, Japan, South Korea and others have urged North Korea to refrain from carrying out the launch, calling it a violation of U.N. Security Council resolutions on nuclear activity because the rocket shares the same technology used for firing a long-range missile. China noted its “concern” and called for calm while citing North Korea’s right to develop its space program.

Past launches have earned North Korea international condemnation and a host of sanctions.

Commercial satellite imagery taken by GeoEye on Dec. 4 and shared Friday with The Associated Press by the 38 North and North Korea Tech websites showed the Sohae site covered with snow. The road from the main assembly building to the launch pad showed no fresh tracks, indicating that the snowfall may have stalled the preparations.

However, analysts believed rocket preparations would have been completed on time for liftoff as early as Monday.

The unexpected launch announcement was issued Dec. 1 as North Koreans began mourning late leader Kim Jong Il, who died on Dec. 17, 2011.

An April launch from the same new launch pad was held on April 13, two days before the centennial of the birth of his father, North Korea founder Kim Il Sung. That rocket broke up just seconds after liftoff.

The U.S. and other nations see the launches as covers for illicit tests of missile technology. North Korea has unveiled missiles designed to target U.S. soil, and has tested two atomic bombs in recent years, but has not shown yet that it has mastered the technology for mounting a nuclear warhead to a long-range missile.

Six-nation negotiations to offer North Korea much-needed aid in exchange for nuclear disarmament have been stalled since 2009.